UBVI PHOTOMETRY AND POLARIMETRY OF V373 CAS

The UBVI photometric and polarimetric observations of the noneclipsing massive binary V373 Cas obtained over the period 1992-1996 are presen ted. The light curve of the star has the same amplitude (similar to 0. (m)10) and shape in all photometric bands, suggesting that the deforma tion of the primary component is mainly responsible for its variabilit y. A variable (with orbital phase) linear polarization has been detect ed in the star. In addition to the second harmonic, there are signific ant (in amplitude) first and third harmonics in the Fourier expansion of the variability of the normalized Stokes parameters. It is shown th at the observed variability most probably arises from the reflection o f light from the surface of the secondary component. An analysis of th e polarimetric data has yielded the orbital inclination of the system, i = 58.degrees 5 +/- 4 degrees. It is concluded that there is an intr insic source of constant linear polarization in the system; a common, nonspherical, gaseous shell could be such a source. The entire body of observational data obtained to date suggests that V373 Cas is a binar y at the very beginning of an active mass-transfer phase.